(107f) Silica Surface Modifications for Bioapplications

Flat silica surfaces were modified for the immobilization of ligands or proteins to be used in a study of protein-ligand and protein-protein binding events on surfaces with low background from non-specific protein binding. A self-assembling monolayer (SAM) of 3-amino-propyl triethoxy silane (APTES) was formed on the silica surface as an initial anchor layer, then short chains of poly(ethylene glycol) with Fmoc protected amine group at one end and carboxyl group at other end were coupled to the silane SAM to reduce nonspecific binding, and finally the amine groups at the end were liberated by Fmoc deprotection, and these will be the active groups used for protein and ligand immobilization. The pK1/2 of the amine group on surface was determined by contact angle titration. The modified surface was also characterized by ellipsometry, X-ray photoelectron spectroscopy (XPS), and time of flight-second ion mass spectroscopy (ToF-SIMS). The amount of protein adsorption on the modified surface was determined by quartz crystal microbalance (QCM).